1. Field of the Invention
The present invention relates generally to the use of boundary layer control for reduced drag on an airfoil shaped wing in combination with augmentation of thrust from a turbojet engine to improve the performance of an aircraft. The increase in performance of an aircraft by reduction of drag and the augmentation of thrust is accomplished specifically in the present invention by the combination of a ventilated wing and an ejector arrangement. The ejector uses the exhaust gases from a turbojet engine carried within the wing to draw air from the boundary layer through the wing, mix the air with the exhaust gases in a mixing chamber, and then exhaust the mixture from the wing thereby providing augmented thrust. Drawing of the air from the boundary layer reduces the drag produced by the wing thereby accomplishing a unique double benefit.
2. Discussion of the Prior Art
Development of boundary layer control devices has been pursued for a number of years. The technique of drawing air from the boundary layer to reduce drag on an aerodynamic shape has been demonstrated using a number of devices. Recently the primary approach for drawing air from the boundary layer has been to provide many very small holes on the surface of the wing or other aerodynamic shape and mechanically pump the air from the surface of the wing.
Current designs to accomplish this technique involve complex ducting techniques to provide airflow from the surface of the wing to the pump adding significant weight to the aircraft. The use of a mechanical or electrical pump requires the use of energy from the aircraft engines. The trade-off of additional weight, power usage, and complexity of the aircraft structure to provide boundary layer control and reduced drag has to date been unattractive for commercial practice.
In addition, the use of a very large number of microfine holes in the wing has distinct disadvantages due to the potential for plugging of the holes and the resultant degradation of performance.
Turbojet engines have been in commercial use for powering of aircraft for a number of years. These engines have been markedly improved over their period of use to provide added thrust and improved fuel consumption. New developments in higher temperature turbine components, increased pressure ratio and engine design technology continue this trend.
Augmentation of thrust for current jet engines takes numerous forms. The primary technique is the use of a high by-pass ratio. The turbojet engine drives a large primary fan which provides first stage compression for the turbojet using a fraction of the air driven through it while the majority of the air by-passes the turbine for direct exhaust and propulsive thrust addition to the direct jet thrust of the turbojet. It has been demonstrated that significant gains in propulsive efficiency are made using this technique.